Dear Son Yl ,

I think it is a height adjustment issue of your set up.

The strong dip at about 4° looks like saturation of the detector.

To my opinion you 'see' the primary x-ray beam between about 4° and about 7°.

Pay attention on the flatness of your sample and a proper height adjustment.

Good luck and

best regards

G.M.

Dear Son Yl

In addition to Dr. Gerhard Martens comment, 7.50 is too high angle for thin film measurement. Thin-film set up of 0.50 is much more usual to the proposal. Nevertheless, low enough for direct beam interference.

You may using a relatively high X-ray beam power, the detector as remembered may saturate.

However, the peak is unusually too large and looks asymmetric, check the collimation and sample position and height as well.

Best regards,

WNM

Sorry, I misunderstood the measurement angle. The effect is observable in angles below 7.5 degrees.

The thin films should be measured at low angle by properly define the experimental conditions. In your case, the high number of counts suggests a saturation of the detector, as already supposed. I suggest to change the slits, verify the alignment of the sample and collect a new pattern. This is not meaningful

thanks everyone for answering